1. Field of the Invention
Aspects of the present invention relate to machine vision inspection. Other aspects of the present invention relate to creating geometric object models for use in machine vision inspection systems.
2. Description of Background Information
For purposes of the disclosure contained herein, a geometric model of an object comprises parameter representations of the geometry of the object. For example, a geometric model of an object may comprise a set of geometric elements, each element comprising an arc or a line defining a substantial part of the object's geometry. Such models have many useful applications. For example, in machine vision inspection, a geometric model of an object can be compared to an object image to facilitate the alignment of the object (e.g., the precise positioning of a surface mount device (SMD) for insertion into a printed circuit board), to check if the object is within specified dimensional tolerances, and to check for other defects. If the inspected object deviates from the geometric model of the object by more than a predefined inspection threshold, that may indicate that the object is defective. Geometric models may be used in other situations. For example, they also may be used to create synthetically animated objects such as those used in video games. A geometric model can be either two dimensional or three dimensional.
In the past, geometric models of objects have been created manually. The process of manually constructing a geometric model of an object may involve entering information concerning the size, the dimension, and the shape of the object. The model may need to be refined before it is used in an inspection process. The refinement process is tedious, labor intensive, and time consuming. For an application in which the objects to be modeled change from time to time, such a manual modeling process is expensive and impractical.
There are commercial products that allow a user to create models of SMDs from their images. A user may manually place features such as corners (e.g., by moving a cursor along the edges at the corner) or leads (e.g., by manually “dragging” a cursor manipulated marquee box) on top of an image of the part to be modeled so that the shape of the parts becomes more evident in the image.